Griff, be sure to order the correct Wilson drop in. The 1991A1 Gov't model takes (believe it or not) the Government model grip safety. Some of the Series 80 Govt's actually use the Commander drop in. Like Templar333 I recently tried a Wilson drop in in my new XSE lightweight Commander and it did not fit. It was too wide to fit in between the tangs on the rear of the frame. I broke the edges on the safety, but it still did not fit. I did not want to mark up my new XSE lightweight frame, so I gave up on it, not wanting to have my tang cut on by a gunsmith to fit another grip safety. Have used these drop in's on a number of guns in the past with excellent results. Does take fitting of the arm, and you should have an idea of what you're doing here (it is a safety). If not, have a smith fit it for you. Any quality hammer (Wilson, Brown, etc) will work with the grip safety.